The present invention relates to a power source system which includes not only a primary power source but also a secondary power source, and more particularly to a power source system used for an apparatus which does not become operable when only a primary A.C. power source is turned on, but is made operable by turning on a secondary power source after the primary A.C. power source has been turned on, for example, a video printer.
In a power source system for an apparatus which is high in frequency of use, it is desirable to keep the secondary power source at an ON-state after the primary A.C. power source has been turned on. While, in a power source system for an apparatus which is low in frequency of use, it is desirable that the secondary power source is usually turned off, but turned on each time the apparatus is operated, because power consumption is reduced. The present invention relates to a power source system which can perform two kinds of operations mentioned above.
FIG. 1 is a block diagram showing a power source system according to a prior art. The power source system of FIG. 1 is used for a video printer which is a controlled apparatus. In FIG. 1, reference numeral 1 designates a power source part, 1a an A.C. input part, 2 a firm-output power circuit, 3 an ON/OFF switching circuit, 3a the movable contact of the switching circuit 3, 4 a system control microcomputer used as a system control part, 5 a first operation switch of the non-lock type, and 6 a controlled circuit (for example, a video printer provided with a memory).
Next, the circuit operation of the power source system of FIG. 1 will be explained.
When an A.C. voltage is supplied from the A.C. input part 1a to the power source part 1, a secondary voltage is applied to the firm-output power circuit 2 and the ON/OFF switching circuit 3, and a stablized voltage is delivered from the firm-output power circuit 2. The stabilized voltage from the power circuit 2 is applied to the system control microcomputer 4 connected to the output side of the power circuit 2. Thus, the system control microcomputer 4 begins to operate.
The ON/OFF switching circuit 3 is previously set so that the initial state of the switching circuit 3 at this time is an OFF-state. Thereafter, the operation switch 5 is depressed. On detecting the operation output of the switch 5, the system control microcomputer 4 delivers a source control signal 7, to put the movable contact 3a in contact with a predetermined, fixed contact, thereby turning on the ON/OFF switching circuit 3. As a result, the secondary voltage is applied to the controlled circuit 6. Thus, the video printer which is the controlled circuit 6, can perform a printing operation with the aid of a switch (not shown).
When it is desired to put the ON/OFF switching circuit 3 back to the OFF-state, the operation switch is again depressed. On receiving the operation output of the switch 5, the system control microcomputer 4 delivers the source control signal 7, to turn off the ON/OFF switching circuit 3 again.
An example of the video printer using such a technique is described in, for example, the September 1989 issue of a Japanese magazine "Television Technology".
As has been explained with reference to FIG. 1, in the above-mentioned prior art, the initial state of the ON/OFF switching circuit 3 (for delivering the secondary voltage) at a time when the A.C. voltage (that is, primary voltage) is supplied, is required to be the OFF-state. Hence, even in a case where the controlled circuit (for example, video printer) is required to become usable immediately after the primary voltage has been supplied, it is necessary to depress the operation switch for the purpose of turning on the ON/OFF switching circuit. Thus, there arises a problem that the controlled circuit is bad in operability and poor in usability.